In a photolithography process of a semiconductor manufacturing process, a semiconductor wafer (hereinafter referred to as a “wafer”) as a target substrate is mounted on a heat plate and is subjected to a heat treatment. As an example of the heat treatment, there is a heat treatment (PEB: post-exposure bake) which is performed after a resist film formed on a wafer is exposed along a predetermined pattern and before development is performed. The shape of a resist pattern formed on a wafer in a photolithography process depends on various factors. One of the factors is a temperature of a wafer in the PEB. In the PEB, the uniformity of a treatment in respective portions within a plane of a wafer is required.
In order to inspect or adjust the heat plate, a temperature measurement wafer including a substrate body and a plurality of temperature sensors installed in the substrate body is mounted on the heat plate and a time transition data of temperatures of the substrate body measured by the respective temperature sensors are acquired. Since the temperature of the substrate body corresponds to the temperature of the heat plate, it is possible to perform the inspection and adjustment of the heat plate based on the time transition data of the temperature thus acquired. Describing the configuration of the temperature measurement wafer, output signals of the respective temperature sensors are transmitted to a measurement unit, which is coupled to the temperature measurement wafer, through, for example, a conductor such as a pattern or wires formed in the substrate body, and are defined as temperature values. Thus, the time transition data of the temperature are obtained.
The temperature measurement wafer is subjected to calibration (graduation) before it is used. Similar to the calibration of a typical thermometer, this calibration is performed by, for example, accommodating a temperature measurement wafer as a calibration target instrument in a thermostatic bath whose atmosphere is stirred into a soaking space, and comparing the temperature measured by each temperature sensor of the temperature measurement wafer with a measurement temperature (standard temperature) indicated by a standard thermometer as a standard instrument.
However, the calibration of an instrument is performed for the purpose of defining the relationship between a measurement value indicated by the measurement target instrument and a measurement value (standard value) indicated by a standard instrument under a specific condition and correcting a deviation of the measurement value of the measurement target instrument with respect to the standard value. The calibration does not necessarily assure the accuracy in the case where the measurement target instrument is used under a condition differing from the condition under which the calibration is performed. In other words, the environment in which the temperature measurement wafer is used differs usually from the environment in which calibration is performed. For example, the temperature measurement wafer is used in the environment in which a temperature gradient exists rather than the environment in which the aforementioned soaking space is formed.
If the environment in which the temperature measurement wafer is used differs from the environment in which calibration is performed, there may be a case where a measurement error is generated between the temperature measured by the temperature sensors and the temperature of the heat plate. Such a measurement error differs for each temperature sensor due to various kinds of factors such as a difference in thermal resistance between the surface of the substrate body and each of the temperature sensors, a difference in heat dissipation through a wire connected to each of the temperature sensors and an individual difference in the shape of the temperature sensors.
In recent years, a resist pattern is required to become further finer. In a wafer heat treatment such as the aforementioned PEB or the like, it is required to accurately control temperatures of the respective portions within the plane of the wafer in the course ranging from the treatment start to the treatment end. In order to execute such control, it is necessary to suppress the aforementioned measurement error and to increase the accuracy of time transition data of a temperature acquired by the respective temperature sensors. In the related art, structures mounted on a substrate body that constitutes a temperature measurement wafer is reduced as much as possible and the adhesion of the wafer and the structures is enhanced, thereby attempting to reduce a measurement error. However, this technique is insufficient to remove the measurement error attributable to the various kinds of factors mentioned above. Furthermore, in the related art, there is proposed a method of removing a measurement error after measurement values measured by temperature sensors are stabilized. However, in the related art, there is not disclosed a method of removing a measurement error before measurement values measured by temperature sensors are stabilized.